Method of extracting a mask pattern for an electron beam exposure

Abstract

In a method of forming a mask from a design pattern, a mask pattern is repeated in the design pattern and is checked about whether or not the mask pattern has the same line width at a border. If the mask pattern having the same line width is divided, a portion having the same line width adjacent to the border is removed from the mask pattern. The removed mask pattern is actually used as the mask for the electron beam exposure. As a result, when electron beam exposure is made by the use of the mask, exposed patterns are partially overlapped with each other at adjacent ones of the exposed patterns and contiguous to each other at portions having different line widths. With this structure, the electron beam exposure is performed without registration errors between the exposed patterns contiguous to each other.

What is claimed is: 
     
       1. A method of pre-processing a mask pattern into a plurality of repeating unit mask patterns each of said unit mask patterns being laid in a predetermined center area surrounded by a boundary area, each said unit mask pattern containing a plurality of pattern segments, each said pattern segment extending across said boundary area into an adjacent unit mask pattern, wherein said boundary area lying between adjacent unit mask patterns is said boundary area for each of said adjacent unit mask patterns, the method comprising: extracting said repeating mask pattern, wherein each said pattern segment has respective first and second preselected widths within said boundary area, thereby forming within said boundary area first and second contiguous rectangular portions of said pattern segment corresponding to said respective widths, wherein said first rectangular portion is further away from said center area;   for each said pattern segment, removing said first rectangular portion from said boundary area to leave a partially removed unit mask pattern having said second rectangular portion; and   using the partially removed unit mask pattern as said pre-processed mask pattern.   
     
     
       2. The method of claim 1, wherein said center area is rectangular. 
     
     
       3. The method of claim 2, wherein for at least one of said plurality of pattern segments said second preselected width ends and said first preselected width begins where said center area ends and said boundary area begins. 
     
     
       4. The method of claim 2, wherein for all of said pattern segments said second selected width is wider than said first selected width. 
     
     
       5. The method of claim 2, wherein said first selected width is the same for each of said pattern segments and wherein said second selected width is the same for each of said pattern segments. 
     
     
       6. A mask for use in electron beam cell projection lithography, said mask having a predetermined center area surrounded by a boundary area, said mask containing a plurality of pattern segments, each said pattern segment having a first preselected width and a second preselected width within said boundary area, thereby forming within said boundary area first and second contiguous rectangular portions of said pattern segment corresponding to said respective widths, wherein said first rectangular portion is further away from said center area; each said pattern segment being arranged in said boundary area so that said first rectangular portion is removed.   
     
     
       7. The mask of claim 6, wherein said center area is rectangular. 
     
     
       8. The mask of claim 7, wherein for at least one of said plurality of pattern segments said second preselected width ends and said first preselected width begins where said center area ends and said boundary area begins. 
     
     
       9. The mask of claim 7, wherein for all of said pattern segments said second selected width is wider than said first selected width. 
     
     
       10. The mask of claim 7, wherein said first selected width is the same for each of said pattern segments and wherein said second selected width is the same for each of said pattern segments.